The invention relates to system for telemetering data. The invention is particularly useful for telemetering the data of, e.g., electrical consumption meters, and is therefore described below with respect to this application.
The modern world functions by means of electrical energy distributed via power supply mains generally operating at an alternating line voltage of 50 or 60 Hz. Most modern equipment is powered by such power supply mains, whereas data communication is usually effected via other channels.
It would be highly desirable to use the power supply mains as the common communication medium, by multiplexing the data from a plurality of consumers to a central receiver. However, such a system requires synchronization between the consumer transmitters and the receiver. This means the transmitter would need a receiver which is very sensitive, narrow-band, and equipped with noise-rejection and error coding/decoding circuitry, and which would therefore make the system very costly.